Yes we got too carried away after our unbeaten season just like Roma were up until a few weeks ago. Ironically Bayern was the team to break our spirit and theirs. We havent played like a big team in Europe since then and I wouldnt be surprised if Roma become super nervous in Europe too.
Lol, if we want to generalize, if there are some fans that don't get "carried away" compared to others are some Juventus fans, that are always super cautious if not pessimistic, most of the times (not my case, but still). Some excitement after 2011-12 season, that is something like an unicum in the history of the sport, is kind of justified, and the Bayern defeat changes nothing to it.
In any case, there are massive differences between us and Roma situations: first of all, we didn't get "trashed". We lost two matches 2-0 and in some parts of them we even gave them competition (and that was Heynckes' Bayern, this Bayern is great but that was something else... Barcelona were far more in difficulty than us, to make an example), and the team responded very well winning the 2013 Scudetto by winning all matches after the elimination. Roma have lost in their home turf conceding 7 goals (I'll throw the stat that in three years we never conceded more than 2 goals in Europe), and aren't fighting back well, they're actually struggling even in the league against small teams. That's also because they won NOTHING before being raped by Bayern, and that doesn't help their confidence.
You say that the Bayern defeat might have affected our spirit in Europe, that's at least very debatable to me. In the unlucky 2013-14 campaign in Champions League, our elimination was due to many factors that are not a lack of spirit, since we dominated most matches and went close even to beating Real Madrid, recording impressive stats. A teams that lacks spirit sits behind and can't create chances (like Roma are doing lately), being outplayed by the opponent. And that would have affected us in the league too, where instead we recorded an historical 102 points. Unfortunately the only important stat that we needed to pass the group, the one of points, was not good enough, but I still believe that without some unfortunate circumstances we'd have got through despite wasting all the chances we've had (refereeing in Madrid, Istanbul snowfest).
For sure, on a gameplay level, our 2013-14 Champions League campaign was better than the 2012-13 one, where except for the Nordsjaelland and Chelsea home games we never shined, but got better results. It happens. Last years' wasted chances and defensive brainfarts are due to bad attitude, not lack of spirit. There's tremendous difference.
If we put it into a bigger perspective, I think that if we advanced from GS in CL we'd have had many difficulties in defending our Scudetto from Roma given their run, and we'd have ended up winning neither (probably the elimination boosted even our will to redeem us and helped us in the second part of the season... Even if EL was not really stimulating for the team, that's what it looked like), but that's personal.
Then lol, how do you say that we haven't played a big team in Europe since then? What would you call Real and Atletico?
Then you said it was our first post-Calciopoli collapse.

Ignoring the fact that it wasn't a collapse, I'd take that as a lapsus and intend that like a post-2011 or post-Conte delusion... Then I agree.
Sorry for the long post dude, but to clarify all the points I had to go deep.